Each satellite that orbits the Earth can have a distinct ephemeris. The ephemeris can include various information, such as the position or orbit of the satellite on a number of dates and times in a regular sequence. Some satellites can use their orbit information for various applications. For example, a satellite's orbit information can be used for altimeter and imaging system applications. A satellite in a global positioning system (GPS) can use its orbit information to provide location and time information anywhere on or near the Earth, where a GPS receiver has an unobstructed line of sight to the GPS satellite.
Satellite navigation systems, such as the GPS, enable a receiver to determine a location from ranging signals received from a plurality of satellites. The ranging signals can be broadcasted on frequencies, such as the L1 signal (1.57542 gigahertz [GHz]), L2 signal (1.2276 GHz), and/or L5 signal (1.17645 GHz). L1 can have a wavelength of about 19 centimeters (cm) and L2 can have a wavelength of about 24 cm. Position can be determined from code and/or carrier phase information. A code division multiple access (CDMA) code is transmitted by the GPS satellites to the receiver and correlated with replica codes to determine ranges to different satellites, which can be used to determine the position of a GPS receiver on or near the Earth. Generally, a GPS receiver receives signals from multiple GPS satellites (e.g., four) to find its position.
Reference will now be made to the exemplary embodiments illustrated, and specific language will be used herein to describe the same. It will nevertheless be understood that no limitation of the scope of the invention is thereby intended.